No sufficient evidence of police misconduct has been found in almost all of the operations into alleged child sex abuse linked to Westminster, an inquiry has heard.

The police watchdog said its probe into allegations of police misconduct in 37 investigations had uncovered no sufficient evidence in 36 of them, while another investigation could not go ahead because the relevant police officer had died.

The Westminster strand of the Independent Inquiry into Child Sexual Abuse (IICSA) is examining whether there was a culture in Westminster of trying to shield people of public prominence from proper investigation.

An Independent Office for Police Conduct (IOPC) report into investigations identified as having a link to Westminster issues states: “In 36 of the 37 operations considered here, no sufficient evidence has been obtained to support allegations of police misconduct.

“Twenty-three of the operations did not identify evidence of the allegation. In eight cases, this was simply because relevant evidence could not be obtained; although of these eight, five of the allegations contained inconsistencies or discrepancies that were potentially undermining. In respect of the other 15 cases, the investigation obtained evidence that undermined the allegations, wholly or in part.

“In one operation, issues regarding an officer attending a police cell containing evidence were identified, however the relevant officer is now deceased and this matter cannot be reasonably progressed any further.”

There were 24 “persons of public prominence” named in the allegations, 16 of whom related to Westminster, the IOPC said.

The late MPs Cyril Smith and Leon Brittan, ex-home secretary, were the two “most frequently” mentioned, with their names cropping up in 11 of the 37 operations.

Seventeen of the investigations were based on allegations made by or information from former police officers, while 13 were made by members of the public and seven were made through the media, the report said.

The bulk of the investigations, which looked at how the probes were conducted rather than whether the allegations themselves were true, focus on the 1970s and 1980s and of the 37, 32 have been completed, the inquiry heard.

Giving evidence at Tuesday’s IICSA hearing in London, deputy senior investigator Chris Mahaffey, from the IOPC, said there appeared to have been a difference in the culture in relation to the police hierarchy at that time.

He said: “I think there was a slight difference in the culture then when compared to the culture now, and I think it probably was the case where more junior officers didn’t think it was their place to challenge or question any decision made by a more senior officer.

“I think that’s changed considerably, but I think it’s nevertheless a theme within many of the 37 investigations.”

However the report warns that while this could increase plausibility of allegations, it is not evidential.

The inquiry heard that the historical nature of the probes meant there were a number of difficulties in investigating, including that some of the relevant people had died, the passage of time made it hard for people to remember details, and that some documents had been destroyed in accordance with whatever was the normal policy of the force at the time.

Mr Mahaffey said while, in most cases there was a willingness from relevant people to help, there have been two instances where police officers have refused to engage in the investigations.

He told the hearing: “There’s one particular officer who has wholly declined to assist, and there is another where one officer initially engaged with us but has declined to assist further, and I think that was prior to him or her making a formal witness statement.”

The inquiry heard 27 of the operations concerned allegations that evidence or lines of enquiry had been suppressed, seven that investigations were stopped or threatened to be stopped, two that someone was charged for a less serious crime than they should have been because of their status, and one that officers had harassed and intimidated a member of the public.

Commander Catherine Roper of the Metropolitan Police’s professional standards said her team’s investigations had found no evidence of misconduct in their own probes.

Ms Roper gave evidence on a report on 17 investigations by the Met’s Operation Winter Key into allegations of non-recent sexual abuse and police misconduct in relation to such investigations.

She said 16 of the 17 cases are closed, while one is almost finished.

She told the inquiry: “No behaviour has been identified that might attract disciplinary action in relation to any of the officers involved.”

She added: “We have absolutely explored every option we have for the investigations.”

Former Home Office minister Lord Taverne told the inquiry he could not recall having come across any allegations of alleged child sex abuse during his time in the post.

He said: “Well, it seems surprising, if I was in charge of the police at the time and of crime, but I can’t recollect any.”

The Westminster strand of the inquiry is expected to sit for three weeks and has already been criticised by the son of the late Labour peer Lord Janner as “a witch hunt against dead politicians”.